22- RESIDUAL DISTRIBUTION OF LEAD, CHROMIUM AND COBALT IN DAIRY PRODUCTS AND THEIR BY-PRODUCTS MANUFACTURED FROM MILK SPIKED WITH THESE METALS

The research study the distribution patterns and residues behavior of Pb, Cr and Co between dairy products [yoghurt, cheese and fatty dairy products ( kishfa, Gaymer and cream)] and their by-products (whey and skim milk) manufactured from experimentally polluted raw ewe̓ s, buffalo̓ s and cow̓ s milk were investigated using Atomic Absorption Spectrophotometer (AAS). The studied metals (Pb, Cr and Co) were concentrated in both cheese and fatty dairy products (kishfa, gaymer and cream) as they recorded concentration factors in cheese produced from raw ewe̓ s, buffalo̓ s and cow̓ s milk of 3.849, 3.466 and 2.452, 3.804, 2.938 and 2.342 and 2.995, 2.682 and 2.336 folds, respectively and 3.693, 3.164 and 2.339, 3.347, 2.773 and 2.242 and 2.601, 2.156 and 2.14 folds, respectively in kishfa, gaymer and cream produced from raw ewe̓ s, buffalo̓ s and cow̓ s milk compared with metals concentrations reported in raw milk used for preparing these products, whereas the by-products of cheese and fatty dairy products processing (whey and skim milk, respectively) contained Pb, Cr and Co concentrations lower than these present in raw milk as they recorded reduction levels of 71.6, 58 and 31.7, 63.7, 39.5 and 27 and 31.4, 20 and 9.5%, respectively in whey and 37.3, 29.9 and 12.1, 41.7, 27 and 19.3 and 21.3, 7.8 and 5.2%, respectively in skim milk. Yoghurt processed from the raw ewe̓ s, buffalo̓ s and cow̓ s milk contained Pb, Cr and Co metals at mean concentration levels similar to and slightly less than those found in raw milk as the reduction levels amounted 0, 0.6 and 1, 0.1, 0.7 and 1.4 and 0.6, 0.8 and 1.9%, respectively. Generally, metals exhibited significant differences (p˂0.05) in their distribution and residues behavior in dairy products and their by-products and comparable to raw milk used in processing as they arranged as follows: cheese> fatty dairy products (kishfa, Gaymer and cream)> raw milk> yoghurt> skim milk> whey, except yoghurt and raw milk which difference was not significant (p˂0.05). Also, metals found in studying dairy products in the order of Pb > Cr > Co, in contrast to their by-products as they arranged reversibly. Finally, metals concentrated in cheese and kishfa produced from raw ewe̓ s milk, in addition to cheese and gaymer produced from raw buffalo̓ s milk at levels significantly higher (p˂0.05) than those present in cheese and cream produced from raw cow̓ s milk.